High resolution ALMA and HST images of q$^1$ Eri: an asymmetric debris disc with an eccentric Jupiter

TL;DR

This study uses high-resolution ALMA and HST images to analyze the asymmetric debris disk around q1 Eri, revealing potential planetary perturbations and inner planetesimal activity, with detailed constraints on disk morphology and composition.

Contribution

First combined ALMA and HST imaging of q1 Eri's debris disk, revealing asymmetries and potential planetary influences, with detailed modeling of disk structure and constraints on gas content.

Findings

Asymmetric debris disk with a broad belt from 34 to 134 au.

Evidence of a possible planet with 8 M⊕ to 11 M_Jup at ~60 au.

No detectable CO gas, with an upper mass limit of 4×10^{-6} M_⊕.

Abstract

We present \textit{ALMA} 1.3 mm and 0.86 mm observations of the nearby (17.34 pc) F9V star q1 Eri (HD 10647, HR 506). This system, with age ${\sim}1.4$ Gyr, hosts a ${\sim}2$ au radial velocity planet and a debris disc with the highest fractional luminosity of the closest 300 FGK type stars. The \textit{ALMA} images, with resolution ${\sim}0.5''$, reveal a broad (34{-}134 au) belt of millimeter emission inclined by $76.7{\pm}1.0$ degrees with maximum brightness at $81.6{\pm}0.5$ au. The images reveal an asymmetry, with higher flux near the southwest ansa, which is also closer to the star. Scattered light observed with the Hubble Space Telescope is also asymmetric, being more radially extended to the northeast. We fit the millimeter emission with parametric models and place constraints on the disc morphology, radius, width, dust mass, and scale height. We find the southwest ansa asymmetry is best fitted by an extended clump on the inner edge of the disc, consistent with perturbations from a planet with mass $8 M_{\oplus} {-} 11 M_{\rm Jup}$ at ${\sim}60$ au that may have migrated outwards, similar to Neptune in our Solar System. If the measured vertical aspect ratio of $h{=}0.04{\pm}0.01$ is due to dynamical interactions in the disc, then this requires perturbers with sizes ${>}1200$ km. We find tentative evidence for an 0.86 mm excess within 10 au, $70{\pm}22\, \mu$Jy, that may be due to an inner planetesimal belt. We find no evidence for CO gas, but set an upper bound on the CO gas mass of $4{\times}10^{-6}$ M$_{\oplus}$ ($3\,\sigma$), consistent with cometary abundances in the Solar System.